Featured Research

Athletes who risk their careers by taking banned growth hormone to improve performance may not be getting the benefits they'd anticipated, according to a new analysis. Researchers pooled data from previous studies in an attempt to summarize what's known about growth hormone's effects on athletic performance.

Share This

Athletes who risk their careers by taking banned growth hormone to improve performance may not be getting the benefits they’d anticipated, according to a new analysis by researchers at the Stanford University School of Medicine.

Related Articles

The team pooled data from previous studies in an attempt to summarize what’s known about growth hormone’s effects on athletic performance. Although this analysis may not reflect the way athletes actually take the drug illicitly, the lead author of the study, Hau Liu, MD, said with growth hormone in the news, it was a good time to scrutinize what was known about the drug.

Athletes’ use of growth hormone is banned by the International Olympic Committee, Major League Baseball and the National Football League. It is also illegal to distribute the drug for the purposes of sports enhancement in the United States. Despite this, athletes have been accused in recent months of taking the drug to boost their strength and performance. One attraction to growth hormone as an athletic enhancer is that it is difficult to detect.

But growth hormone may not deliver the benefits some athletes expect. “What we saw is that while there was a change in body composition, that didn’t translate to an improvement in performance,” said Liu, who was a clinical scholar in endocrinology at the time of the study.

The group searched the medical literature as far back as 1966 looking for studies that tested the physiological effects of excess growth hormone compared with a placebo in healthy people. To be included, the studies had to be double-blinded—neither the participants nor the researchers could know which participants received growth hormone and which received placebo. They excluded studies involving people with growth hormone deficits caused by pituitary tumors or other conditions. In those people, bringing growth hormone up to normal levels does improve strength.

They found 27 studies with a total of 303 participants that fit the bill. When they combined data from these independent studies looking at the effects of growth hormone in healthy people, the picture it painted wasn’t good for growth hormone.

Overall, people who received growth hormone did seem to have more lean body mass, which is generally associated with more muscle. However, during exercise the people who got growth hormone in some of the studies generated more lactate—the byproduct of exercise that can cause muscle fatigue. In one study, two cyclists who received growth hormone weren’t able to finish a workout because of fatigue.

Only two of the studies with a total of 38 participants looked at muscle strength in people who took growth hormone; they took it for six weeks in one trial, and 12 weeks in the other.

Despite having more lean body mass, the people didn’t appear to be any stronger after receiving the drug. Studies examining other measures of athletic performance, such as VO2max, which is a measurement of how much work the muscles can do, also revealed no improvement.

“The key takeaway is that we don’t have any good scientific evidence that growth hormone improves athletic performance,” said senior author Andrew Hoffman, MD, professor of endocrinology, gerontology and metabolism.

However, Hoffman urged caution in interpreting the data, given the embarrassment endocrinologists faced in the 1980s when they’d warned that testosterone had no performance-enhancing effects. Later studies testing doses at the levels athletes actually took clearly showed a performance boost from the drugs. With that in mind, the group is careful to warn that their findings only summarize the studies that have been done to date and may not represent the way athletes actually take the drugs.

The studies in this analysis examined people after only a single dose of growth hormone or up to three months of treatment; in all of the studies, the doses were lower than anecdotal reports of the doses athletes actually take. Athletes aren’t talking openly about how much of the hormone they take, but Liu said some estimates are that the illicit dose is as much as five times what was given in the studies. What’s more, athletes combine the hormone with other supplements, steroids and increased training, all of which could alter the effects of growth hormone.

Liu, who is now in the division of endocrinology and metabolism at the Santa Clara Valley Medical Center, said even if there’s no physiological data that growth hormone helps performance, it may still give athletes an edge psychologically. If an athlete appears more muscular, the boost in self-confidence from that alone might be enough to spur them to hit the baseball farther or cycle faster.

“So much of athletic performance at the professional level is psychological,” said Hoffman, who is also chief of endocrinology at the Veterans Affairs Palo Alto Health Care System.

Liu and Hoffman said that to learn the effects of real-world growth hormone supplementation, they would first need to know how much of the drug athletes were taking and for how long, on average. A large trial testing these doses in athletes would be difficult to conduct, they said. The side effects alone might make the trial ethically troublesome. The cost of growth hormone would also make the trial expensive unless companies donated the drug, which is unlikely.

The work will be published in the March 18 online version of the Annals of Internal Medicine and in print on May 20. Other Stanford researchers involved in the trial include senior research scientists Dena Bravata, MD, and Anne Friedlander, PhD; Ingram Olkin, PhD, professor emeritus of statistics; clinical fellows Vincent Liu, MD, and Brian Roberts, MD; medical fellow Eran Bendavid, MD, MPH; biostatistician Olga Saynina, MA, MBA; and Alan M. Garber, MD, PhD, the Henry J. Kaiser Jr. Professor.

The study was funded by the Agency for Healthcare Research and Quality, a National Research Service Award, Department of Veteran Affairs, Stanford University Medical Center, Stanford University, Genentech Inc., the National Science Foundation and the Evidence-Based Medicine Center of Excellence of Pfizer.

More From ScienceDaily

More Health & Medicine News

Featured Research

Mar. 3, 2015 — New assays can detect malaria parasites in human blood at very low levels and might be helpful in the campaign to eradicate malaria, reports a new study. An international team led by Ingrid Felger, ... full story

Mar. 3, 2015 — Adults over the age of 30 only catch flu about twice a decade, a new study suggests. So, while it may feel like more, flu-like illness can be caused by many pathogens, making it difficult to assess ... full story

Mar. 3, 2015 — No significant change in home habits of smokers have been observed in the aftermath of a ban on smoking in public spaces, researchers report. Greater inspiration to kick the habit likely comes from ... full story

Mar. 3, 2015 — Heart function has been associated with the development of dementia and Alzheimer's disease through a new study. Participants with decreased heart function, measured by cardiac index, were two to ... full story

Mar. 3, 2015 — Children of recently separated or divorced families are likelier to drink sugar-sweetened beverages than children in families where the parents are married, putting them at higher risk for obesity ... full story

Mar. 3, 2015 — Gastric bypass and similar stomach-shrinking surgeries are a popular option for obese patients looking to lose weight or treat type 2 diabetes. While the surgeries have been linked to a decreased ... full story

Mar. 3, 2015 — Most people consume more salt than they need and therefore have a higher risk of heart disease and stroke, which are the two leading causes of death worldwide. But a new study reveals that dietary ... full story

Mar. 3, 2015 — Twice as many children born to mothers who took antibiotics during pregnancy were diagnosed with asthma by age 3 than children born to mothers who didn’t take prenatal antibiotics, a new study has ... full story

Mar. 3, 2015 — Although sedatives are often administered before surgery, a randomized trial finds that among patients undergoing elective surgery under general anesthesia, receiving the sedative lorazepam before ... full story

Featured Videos

Mom Triumphs Over Tragedy, Helps Other Families

AP (Mar. 3, 2015) — After her son, Dax, died from a rare form of leukemia, Julie Locke decided to give back to the doctors at St. Jude Children&apos;s Research Hospital who tried to save his life. She raised $1.6M to help other patients and their families. (March 3)
Video provided by AP

Looted and Leaking, South Sudan's Oil Wells Pose Health Risk

AFP (Mar. 3, 2015) — Thick black puddles and a looted, leaking ruin are all that remain of the Thar Jath oil treatment facility, once a crucial part of South Sudan&apos;s mainstay industry. Duration: 01:13
Video provided by AFP

Woman Convicted of Poisoning Son

AP (Mar. 3, 2015) — A woman who blogged for years about her son&apos;s constant health woes was convicted Monday of poisoning him to death by force-feeding heavy concentrations of sodium through his stomach tube. (March 3)
Video provided by AP

Related Stories

Dec. 5, 2012 — The drug erythropoietin, often called EPO, is banned from sports because it is believed to enhance an athlete's performance and give people who use it an unfair advantage over unenhanced ... full story

June 11, 2012 — Sportsmen and women have been known to dope with the blood hormone Epo to enhance their performance. Researchers have now discovered, through animal testing, that Epo has a performance-enhancing ... full story

Oct. 1, 2010 — Growth hormone has multiple effects on skeletal muscle, including promoting growth and regeneration. It is not clear, however, which effects are direct and which are mediated via induction of the ... full story

June 29, 2010 — UK scientists show for the first time that high doses of caffeine directly increase muscle power and endurance during sub-maximal activities, which in humans ranges from everyday activities to ... full story

May 3, 2010 — A new study finds that human growth hormone (HGH) improves sprint capacity in healthy recreational athletes. This is the first trial to demonstrate that HGH improves athletic ... full story

ScienceDaily features breaking news and videos about the latest discoveries in health, technology, the environment, and more -- from major news services and leading universities, scientific journals, and research organizations.